The report released this week by the world's leading climate scientists made no bones about it: Global warming is happening in a big way and it is very likely manmade. The U.N. report that came out soon after made a critical point: "The livestock sector emerges as one of the top two or three most significant contributors to the most serious environmental problems, at every scale from local to global." And yet, so many environmentalists continue to eat meat. Why?

Being part of the solution can be a whole lot simpler -- and cheaper -- than going out and buying a new hybrid. We can make a huge difference in the environment simply by eating a plant-based diet instead of an animal-based one. Factory farming pollutes our air and water, reduces the rainforests, and goes a long way to create global warming. Yet for some environmentalists, the idea of giving up those chicken nuggets is still hard to swallow.

So, I thought I might discuss a few of the key concerns that my meat-eating friends offer in defense of their continued meat consumption. Here we go:

Some were worried about thriving, physically, on a vegetarian diet.

Now this just does not make sense. Half of all Americans die of heart disease or cancer and two-thirds of us are overweight. The American Dietetic Association says that vegetarians have "lower rates of death from ischemic heart disease; ... lower blood cholesterol levels, lower blood pressure, and lower rates of hypertension, type 2 diabetes, and prostate and colon cancer." Vegetarians, on average, are about one-third as likely to be overweight as meat eaters.

And I've just learned from the brilliant Dr. Andrew Weil that there is something called arachidonic acid, or AA, in animal flesh that causes inflammation. AA is a pro-inflammatory fatty acid. He explains that "heart disease and Alzheimer's -- among many other diseases -- begin as inflammatory processes. The same hormonal imbalance that increases inflammation increases cell proliferation and the risk of malignant transformation." They are finding out that inflammation is key in so many of the diseases that plague us. So when you eat meat, you ingest AA, which causes inflammation, which fires up the disease process. It doesn't matter if the chicken is free range or the beef is grass-fed because the fatty acid is natural and inherent in the meat.

As for having strength and energy on a vegetarian diet, some of the world's top athletes are vegetarian. A few examples: Carl Lewis (perhaps the greatest Olympian of all time), Robert Parish (one of the "50 Greatest Players in NBA History"), Desmond Howard (Heisman Trophy winner and Super Bowl MVP), Bill Pearl (professional bodybuilder and four-time Mr. Universe), Jack La Lanne (Mr. Fitness himself) and Chris Evert (tennis champion). Vegetarian athletes have the advantage of getting all the plant protein, complex carbohydrates and fiber they need without all the artery-clogging cholesterol and saturated animal fats found in meat that would slow them down. In fact, Carl Lewis says that "my best year of track competition was the first year I ate a vegan diet."

One person pointed out that the rain forest is being cut down to grow soy, not meat.

Actually, much of the rain forest is being chopped down for grazing, but also yes, the rain forest is being chopped down to grow soy -- but not for human consumption. Americans and Europeans can't raise all the feed domestically that is needed to sustain their meat addictions, so agribusiness has started cutting down the rain forest. Ask Greenpeace or any other environmental group, and they'll tell you that the overwhelming majority of soy (or corn or wheat, for that matter) is used to feed animals in factory farms. In fact, Greenpeace recently unveiled a massive banner over an Amazon soy field that read, "KFC-Amazon Criminal," to accentuate the point that large chicken and other meat companies like KFC are responsible for the destruction of the Amazon. It takes many pounds of soy or other plant foods to produce just one pound of animal flesh -- so if you're worried about the rain forests being chopped down for grazing or to grow soy, your best move is to stop eating chickens, pigs and other animals. If more people went vegetarian, we would need far less land to feed people, and we wouldn't have to destroy the few natural places that this world has left.

Some wondered about humane, organic or kosher meat.

Sadly, most of the meat, egg and dairy companies that pretend to be eco- or animal-friendly, with packages covered in pictures of pretty red barnyards, are basically the same massive corporately owned factory farms but with a newly hired advertising consultant. In fact, labels like "Swine Welfare" and "UEP Certified" are simply the industry labels that attempt to hide the horrible abuse involved in these products' production. And even "organic" farms are industrializing in ways that shock the journalists who bother to investigate. Sadly, "kosher" means nothing when it comes to how animals are treated on farms, and the largest kosher slaughterhouse in North America was caught horribly abusing animals -- ripping the tracheas out of live cows' throats and worse -- and defending the abuse as kosher.

All that said, it's undeniable that the rare meat eater who limits himself or herself to a bit of grass-fed cattle flesh on occasion is making a much smaller environmental impact than the vast majority of Americans. But when you consider that no reputable scientific or medical body believes that eating animals is good for us, let alone necessary, one has to wonder about environmentalists who insist on consuming products that we know to be resource-intensive and polluting (even if they're less resource intensive and polluting than some other similar options or eaten in "moderation"). It'd be like driving an SUV that gets 15 mpg rather than 10, or driving an SUV three days per week instead of seven. Sure, it might be better for the environment, but with so many more fuel-efficient ways to get from A to B, there's no need to drive any SUV at all. Eating meat -- any meat -- is the same thing: With so many healthy vegetarian options that are kinder and far more eco-friendly than even the "best" meat products, there's just no good justification for someone who claims to be an environmentalist -- or to oppose cruelty -- for doing it.

Some worry about "preachy" or "judgmental" or "extreme" vegetarians.

And some consider the very choice to be a vegetarian to be extreme. Although I certainly don't like radical in-your-face messages, the truth is that, sometimes, it's the only thing that seems to wrench us out of our slumber. I know it worked with me when I saw one of the slaughterhouse videos -- definitely not pleasant, but it got my attention.

The very nature of progressive movements throughout history is to tell others to stop doing something harmful or degrading (e.g., using humans as slaves, sexually harassing women, forcing children to work in sweatshops, harming the environment, etc). Yes, the abolitionists, suffragists, feminists, and civil rights activists were called extreme, and similarly, some vegetarians are called extreme. But maybe it's just because vegetarianism is not yet a cultural norm. Old habits -- and appetites -- die hard, and there is usually a lot of resistance before things change. I'm a southern gal, and I loved my chicken fried steak like no other. I didn't want to give up the joys of Sunday barbecue or chicken wings with my friends on a Friday night. I get it; I understand.

But still, if we are to continue evolving -- physically, emotionally, and spiritually -- we really do have to look at how our dinner choices affect not only the environment but, even more importantly, the well-being (or intense suffering) of other creatures. So yes, on the one hand, the move to eating a plant-based diet may look extreme because most people don't do it. But on the other hand, we can still have our barbecued (soy dogs and veggie burgers) and feel good about it.

I do feel strongly that vegetarians should not play into the self-righteous stereotypes, that we should not be shrill or judgmental, of course, but that doesn't require silence; it simply requires patience and decorum.

A few people asked about meat in the developing world, or meat for Eskimos or Inuit.

If you are an Eskimo, or you're living in sub-Saharan Africa and you're reading this blog, I'm not going to begrudge you your pound of flesh; it would be silly of me to do so. But if you're reading this in a developed country where almost all animals are eating animal feed rather than grazing, are factory-farmed rather than living with families or hunted, and you have abundant vegetarian options all around you, talk of people who have limited food options doesn't apply to you.

Some people worried that it's hard to be a vegetarian.

Being vegetarian isn't exactly the supreme sacrifice -- surfing around the food pics on any vegetarian cooking site will show you that. Vegetarian and vegan food is everywhere (even Burger King has a veggie burger!). Most, if not all, major grocery stores carry soy milk, mock meats ("chicken" nuggets, BBQ "ribs," burgers, soy "sausage," etc.), vegan cheeses, and soy ice cream. If you can't find what you want at the store, most will order it for you. Many restaurants have veggie options a-plenty (especially Thai, Indian, Ethiopian, Mexican and other ethnic restaurants, which are my favorite anyway). Sure, some vegetarians may prefer not to eat food that was cooked on the same grill as meat, but I'm not concerned about that (it does not cause more animals to suffer or more environmental harm). You can find great vegetarian recipes at www.VegCooking.com.

I'd also like to address the top five most common justifications that I hear from meat eaters for their meat consumption:

No. 5: "Humans have always eaten animals -- it's natural."

First, our evolution in human morality is marked almost entirely by our attempt to move beyond the "might makes right" law of the jungle. It may indeed be "natural" for the powerful to dominate the weak, but that doesn't mean we should support it.

Second, human bodies don't require meat to be healthy -- quite the opposite. Animal flesh contains cholesterol and saturated fat, which are hard on our bodies. We may have had a need to eat meat thousands of years ago, in times of scarcity as hunter-gatherers, but we don't need to now, and we'll be better off if we don't. Check out this essay by Dr. Milton Mills for more information on the issue of whether the human physiology is designed for meat consumption.

Most critically, the people who say this generally use it to justify buying the same old meat that comes from giant, wholly unnatural factory farms where animals are crammed into filthy sheds or cages and not allowed to do anything natural to them -- at all, ever (breathe fresh air, bask in the sun, raise their young, dust-bathe, form social orders, etc.). Chickens in the egg industry have half their beaks cut off, piglets in the pork industry have their tails cut off, etc. (Please take 10 minutes to watch the video at www.Meat.org.) This is how 99 percent of chickens and turkeys, 95 percent of pigs and eggs, and most cow flesh and dairy products end up on our plates.

Lastly, if you care so much about being "natural," then think for a moment about the harm that you're doing to your natural environment by eating meat -- any meat. At the end of the day, for me, we don't need to eat meat, we'll be better off without it, and it causes animals to suffer.

No. 4: "Animals are not equal to humans, so we should not be so concerned about them."

I disagree with Princeton professor Peter Singer on many issues, but on this one I think he gets it precisely right. Writes Dr. Singer, "[W]hen nonvegetarians say that 'human problems come first,' I cannot help wondering what exactly it is that they are doing for human beings that compels them to continue to support the wasteful, ruthless exploitation of farm animals." Which is to say: Fine, don't spend any time at all on animal issues, but please don't pay other people to abuse animals, which is what you are doing when you buy chicken, pork or other animal products. And remember: A vegetarian diet is also the best diet for the planet, so eat as though the planet depended on it, since it just might.

No. 3: "There have been many brilliant meat eaters, like Picasso and Mozart, so they could not have been wrong."

I highly doubt that anyone is going to suggest that vegetarians Steve Jobs, Leonardo da Vinci, Pythagoras, Albert Einstein, Leo Tolstoy or Mohandas Gandhi were especially brilliant because they were vegetarians, and I also don't think one can make the argument that meat eaters attained their great heights as a result of their diet. Interestingly, studies show that vegetarians are smarter than meat eaters, but there is probably not causality there -- it's probably just that thoughtful people tend to question things more deeply, hence the decision to become vegetarian. Here's a 2006 study from the British Medical Journal about vegetarians being smarter than meat eaters.

No. 2: "Where do you draw the line? Should we protect insects? What's the difference between killing plants and killing animals? They're all alive."

The theologian and Narnia inventor C.S. Lewis staunchly opposed testing on animals on Christian grounds, and he pointed out to those who asked this question that the question is baseless -- they already know and understand the differences between plants and animals. To whit, every reader will recoil in horror if asked to imagine lighting a cat on fire or beating a dog's head in with a baseball bat -- because we know that these things cause the animals pain. But none of us feels similarly at the prospect of pulling weeds or mowing our lawn -- because we know that weeds and lawns have no capacity to feel pain. Chickens, pigs, fish and cattle all feel pain in the same way and to the same degree as any dog or cat. Just watch their faces and their body language in these undercover videos; listen to their animal versions of screaming. I assure you, grass does not suffer like these poor creatures do.

I'm not so sure about insects, though I try to give them the benefit of the doubt whenever possible. Yes, when I walk down the street, I'm sure I step on bugs. But does the fact that I can't stop all cruelty mean that I shouldn't bother to stop a lot of it? Of course not. That'd be like saying that if you drive a car, you shouldn't even bother to recycle.

And the No. 1 justification for eating meat is: "Meat won't kill me, and I like it."

No question -- this is the crux of it all, the only purely honest answer if you ask me. Sure enough, unless you get really bad food poisoning from your next piece of undercooked chicken or choke to death on a piece of steak, meat won't kill you right away. But chances are pretty good that eating meat could reduce your life span (and quality) in the long run. The American Dietetic Association (the overarching group of nutrition researchers, doctors, etc.) says that vegetarians have lower rates of heart disease, cancer, diabetes and obesity than do meat eaters. Some argue that for every study, there's another that says the opposite, but that's simply not so in this case. You'd be hard-pressed to find a reputable scientific or medical body that disagrees with the simple fact that vegetarians are a fraction as likely to be overweight and much less likely to suffer from heart disease and cancer. Really, even if I didn't give a hoot about animal suffering or environmental degradation, I would still be vegetarian because the diet is the best diet for my health. And as noted, eating meat does support cruelty to animals and environmental degradation, all for the sake of a palate preference (which, by the way, can be largely satisfied by the luscious faux meat options out there).

Concluding thoughts:

One thing about being a vegetarian that is often missed is how empowering it is. Personally, I think that integrity of action requires that among other things, we attempt to lead lives that are as compassionate and conscious as possible. What this means to me, personally, is that if there is something that I would not want to do myself, I don't feel good paying someone else to do it on my behalf. So I don't inflict suffering or kill animals myself; and I don't support the market of killing by buying these poor animals chopped up and shrink-wrapped in the grocery store either.

We are a nation of animal lovers, and we all cringe in horror when we hear about cases like a dog being burned alive or tossed into freeway traffic. But chickens and pigs and other animals also deserve our compassion. They are all smart animals who feel pain and fear, yet they are treated just horribly, and sadly, there are no laws to protect them. Don't take my word for it, watch Alec Baldwin's Meet Your Meat and see for yourself what goes on.

We oppose sweatshops and child labor, and we cringe at the thought of children laboring in developing countries. But American slaughterhouses are sweatshops. They employ people working illegally who can't defend themselves out of fear of being deported. Conditions in these places are so bad that the average annual turnover rate for slaughter-line workers is out of sight. Check out the website of this labor organization to learn about its fight against Smithfield Foods (the world's largest pork and turkey producer, which owns Butterball).

We are environmentalists, and we cringe when see a bright yellow Hummer in the grocery store parking lot. But regardless of the amount of fuel that a Hummer uses or the amount of greenhouse gasses that it emits, if we're eating meat, we're making a conscious decision that is even more wasteful and polluting.

Americans and Europeans eat meat because we want to, not because we have to. And we do it at the expense of animals, people and the environment.

We would do well to consider a dietary change.

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